Field of the Invention
The present invention relates to a liquid discharge apparatus, an imprint apparatus, and an article manufacturing method.
Description of the Related Art
As one of printing methods, an ink jet system for discharging droplets from a recording head has been developed, and such an ink jet system has recently been used in various fields. There are some cases of providing liquid discharge apparatuses with liquid tanks that regain liquid to be discharged from recording heads. Particularly in liquid discharge apparatuses for industrial uses, there is a desire to measure a remaining amount in liquid tanks, and notify users of replacement time of the liquid tanks, thereby allowing the users to replace the liquid tanks, thus reducing downtime of the apparatuses, resulting in enhancement of productivity of the apparatuses.
Japanese Patent Laid-Open No. 2000-190520 discloses a configuration of radiating light from a light-emitting unit into a flexible liquid tank so as to optically measure displacement of a position of a liquid level that is an interface between gas and liquid in the liquid tank based on change in light income on a light receiving unit. Japanese Patent Laid-Open No. 2008-105360 discloses a configuration of generating buoyancy by filling a floating bag with a filler whose density is smaller than that of a liquid filled in a container, thereby urging a flexible member in a direction to increase a volume of an ink chamber so as to apply a negative pressure to an ink.
The liquid discharge apparatus disclosed in Japanese Patent Laid-Open No. 2008-105360 generates buoyancy by filling the floating bag with the filler whose density is smaller than the density of the liquid filled in the container. Unfortunately, there is no description regarding how to measure a remaining amount of the liquid in the container in Japanese Patent Laid-Open No. 2008-105360. Meanwhile, the liquid discharge apparatus disclosed in Japanese Patent Laid-Open No. 2000-190520 optically measures displacement of the liquid level in the flexible liquid tank where there exists an interface between gas and liquid. However, in a liquid discharge apparatus in which a flexible film is provided in a container to separate the container, and a liquid filler is introduced into one of the separated containers, and a liquid is introduced into the other separated container, there exists no interface between gas and liquid; therefore, it is impossible to optically measure a position of the liquid level. This means that the method of measuring the position of the liquid level as disclosed in Japanese Patent Laid-Open 2000-190520 is inapplicable to such a liquid discharge apparatus.